WASHINGTON — Leading Senate Democrats have put the Bush administration on notice that they intend to press for a fuller accounting on a wide range of counterterrorism programs, including wiretapping, data-mining operations, and the interrogation and treatment of detainees.

Democrats have appeared divided at times over how aggressively to challenge the administration on its terrorism policies, in part because of concern that they risked playing into Republican accusations that they were soft on terrorism.

But Senator Patrick Leahy, a Democrat from Vermont, who will take over next month as chairman of the Judiciary Committee, made clear at a committee hearing on Wednesday that he wanted to actively investigate the effectiveness and legality of many programs.

"The administration's gone to unprecedented lengths to hide its own activities from the public while at the same time collecting an unprecedented amount of data on private citizens," Leahy told Robert Mueller 3rd, the director of the FBI.

As the sole witness at the hearing, Mueller bore the brunt of the Democrats' criticism. But their sharp questions often went well beyond the FBI's purview, delving into areas like the National Security Agency wiretapping program, CIA interrogations of Al Qaeda suspects and the Department of Homeland Security's use of profiling scores to assess the risks posed by travelers.

As a first step toward what Leahy described as an effort to roll back the administration's curtailment of rights, he and Senator Arlen Specter, a Republican from Pennsylvania, proposed legislation that would seek to restore the rights of all terrorism suspects to challenge their detentions in court.

The military detention legislation that President George W. Bush signed into law in October stripped the federal courts of jurisdiction to hear petitions from noncitizens for rights of habeas corpus. Brian Roehrkasse, a spokesman for the Justice Department, said that while the administration would review the Leahy-Specter proposal, the process approved by Congress allows enemy combatants to challenge their detention and "goes well beyond what is required for lawful prisoners of war under both international and domestic law."

Several Republican senators on the Judiciary Committee, including Specter and Charles Grassley of Iowa, told Mueller that they shared Democratic concerns about some terrorism operations, particularly the FBI's struggle to remake its computer system. An audit of the computer overhaul released earlier this week by the Justice Department inspector general found that the project risked falling short in funding by $57 million this year. But Mueller disputed that account on Wednesday, saying that the program was on schedule and within budget.

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In addition, several senators criticized the pace of the FBI investigation into the unsolved anthrax attacks of October 2001, and the bureau's unwillingness to fully brief members of Congress about where the investigation stands.

Amid the sharp criticism, one notable dissent came from Senator Jeff Sessions, a Republican from Alabama, who thanked Mueller for his hard work and suggested that Democrats and civil- rights advocates were too quick to criticize the administration over policies that might affect privacy rights.

Opponents of the administration's policies, Sessions said, will "criticize you for not maintaining information and not sharing it with the person at the airport so they can identify somebody who might be a terrorist if they happen to get by the system, and then they'll complain that you're maintaining information that somehow might oppress somebody's rights."

The senator added that "if you don't maintain those records and somebody slips by and kills a lot of Americans, you'll be hauled in here to be criticized for it, there's no doubt about that."

Leahy said that he was troubled by recent reports about the Department of Homeland Security's use of a scoring system to determine the terrorist or criminal risk of people entering the United States. He said that the program, and broader government data-mining efforts, could make it more difficult for innocent Americans to travel or get a job - without giving them a chance to know why they were labeled a risk.

"It's worrisome," the senator said, "because if it's done poorly or without proper safeguards and oversight, databanks don't make us safer, they just further erode Americans' privacy."